一番 (ICHIBAN)

I think what you wanted to say is "the first" of "my first note". In Japanese, saying はじめてのノート sounds a bit more natural. "Ichiban" sounds like "No.1". 

This is my first notebook entry. (--> これはわたしのはじめてのノートエントリーです。)
I don't really know what I'm a supposed to practice, since I haven't even done a italki lesson yet.

Kyou wa nichiyoubi desu.
今日は日曜日です。
きょうはにちようびです。 (Perfect!)

Watashi wa nooto o kaite imasu.
私はノートをかいています。(Perfect!)

I know a lot of hiragana (if not all).
I know a little bit of Kanji.
I know very little when it comes to katakana. （ストキシ）

Eto...

さようなら

Good job! It's OK learning by yourself with help of other people here on italki, of course taking lessons with teachers is good, too. Please enjoy learning Japanese. Good luck to you.